An adhesive is a substance capable of holding solid materials (e.g., adherents or substrates) together by surface attachment. Pressure sensitive adhesives (PSAs) generally are adhesive materials which bond to adherents when a required pressure is applied to effect an adhesion to the adherents. PSAs can be permanent or removable. Removable PSAs have been widely used in re-positionable applications, such as post-it notes. Pressure sensitive adhesives are generally based on a polymer, a tackifier and an oil. Some common PSAs are based on polymers such as natural rubbers, synthetic rubbers (e.g., styrene-butadiene rubber (SBR) and SIS), polyacrylates, polymethacrylates, and poly-alpha-olefins. The PSAs can be solvent-based, water-based, or hot melt systems.
Hot-melt adhesives at ambient temperature are generally solid materials that can be heated to a melt to hold adherents or substrates together upon cooling and solidifying. In some applications, the bonded substrates can be detached by remelting the hot melt adhesive if the substrates can withstand the heat. The hot melt adhesives can be used in paper products, packaging materials, laminated wood panels, kitchen countertops, vehicles, tapes, labels, and a variety of disposable goods such as disposable diapers, hospital pads, feminine sanitary napkins, and surgical drapes. These hot melt adhesives are generally based on a polymer, tackifier, and a wax. Some common hot melt adhesives are based on polymer components including ethylene based semi-crystalline polymers such as ethylene-vinyl acetate copolymer (EVA) and linear low density polyethylene (LLDPE), styrene block copolymers (SBC) such as styrene-isoprene-styrene (SIS) copolymer and styrene-butadiene-styrene (SBS) copolymer, ethylene ethyl acrylate copolymers (EEA), and polyurethane reactive adhesives (PUR). One desirable property of hot melt adhesives is the absence of a liquid carrier, thereby eliminating the costly process associated with solvent removal.
Some compositions that contain a polymer, a tackifier and optionally at least a filler or a pigment may be used as thermoplastic marking compositions. The polymer can be a silane-modified petroleum resin, an ethylene-vinyl acetate copolymer, an atactic polypropylene; a carboxy-modified hydrocarbon resin, an ester-modified hydrocarbon resin, a polyolefin copolymer, or a combination thereof.
Olefin block copolymers (OBCs) have been found to be advantageous in a variety of adhesive applications such as described, for example, in U.S. Pat. No. 7,524,911 and U.S. Pat. No. 7,989,543 as well as in US Patent Application Publication No. 2011-0262747.
It would be desirable to provide further improved compositions wherein the compositions have an improved open time, where open time refers to the set up time of an adhesive, or the time it takes for the adhesive to solidify. Delays in the open time allows for increased time for adhesive wetting and bonding. The current market trend is to operate machinery at higher line speeds and at lower temperatures, so it would be desirable to be able to apply the adhesive at a lower temperature (100-120° C.) and still maintain the bonding performance required.